Hmm, it's weird especially if you take into account how little I like about the MBA. But this is something I really like about the MBA (wishing it would spread wildly):
Since a lappy is crap soundwise, what's the use of speakers? As I see it, it's for playing OS-warnings and that sort of thing, for watching a short clip and not much else. That way, a single speaker is more than enough.
I could do without any, as it is. I even have all my UI-sounds off. And I never use my MBP without headphones (well, I do just not for audio, and I always carry atleast one set of headphones).